Understanding the Chemistry of Dye Sensitized Solar Cells

Seminar title: Understanding the Chemistry of Dye Sensitized Solar Cells (or: What to do when high-vacuum surface science and femto second lasers don’t give useful results.) Dye Sensitized Solar Cells (DSSCs) are of interest as a lower cost and faster production alternative to silicon photovoltaics In the simplest description, DSSCs transform sunlight to electricity using a dye monolayer at the interface between TiO2 nano-crystals and an organic electrolyte. Research on DSSCs has been increasing for over 20 years, with over 100 groups world wide contributing at some level. Unfortunately, finding anything concrete in the >3000 papers on the subject can be quite difficult. DSSCs have turned out to be much more complex than initially anticipated. A typical DSSC cell now contains 9 intentional molecular components, along with water and other more minor impurities (figure 1). This can be compared to 3 elements (silicon and two dopants) in the active layer of a silicon PV cell. The components in DSSCs have been designed so that they interact, in known ways, to improve function. Conceptual models and measurement techniques have tended to assume that in all other ways the components are "non - interacting". Recently we and others have found that the assumption of noninteraction can be spectacularly false In part because of these interactions, attempts to define DSSCs in terms of measurements made on ideal systems or on isolated subsets of full DSSCs have often been unsuccessful. At Imperial College we have been studying DSSCS using only tools which can be applied to complete solar cells. Using this approach, and the philosophy that simple measurements on cells with varying chemistry can give more information than complex measurements on a single sample, we have begun to reform the model of how DSSCs work. This talk will describe our measurements and our results. I will attempt to cover the basic chemistry of DSSC cells, focus in on the most interesting reactions in DSSCs, and then show how previously unappreciated interactions between components can effect these reactions. For more information about this seminar, please contact: Mike Apte(510) 486-4669

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